Looking for advise. Especially from those who leave in Northern hemisphere - Ontario / Northern USA and who have experience keeping squirrels over the winter for release in the Spring.

First some info:

Squirrel was born in early August, so it has just grown up and we cannot release it as there are no leaves on the trees and it is not ready in terms of nest and experience gathering food.
We keep it in our sun room. So it is safe from wind, rain, snow and extreme temperatures, but it is getting colder there as season is changing.
Sun room is prepared as we have some dirt, leaves and a lot of interconnected branches for running and training.
It build it's own nest behind a cabinet.
We gathered a lot of natural food - acorns, maple seeds, hickory and black walnuts.

Questions:

- Is the setting OK for winter? Or it will be too cold? I don't think temperatures go below freezing and definitely not to -10, -15 degrees Celsius (14, 5 Fahrenheit)
- We plan release in April, probably the second part of April. Is it too soon? Should we wait for better weather? April can be cold. Should we wait for some leaves on the trees?
- We plan to keep minimal contact for 30 days before the release - any advise here?
- In regards to contact. Squirrel is very friendly and attached to us (my wife and myself). It is 12-13 weeks old now, so I think it is a grownup. And we worry about that. She may not be afraid of people. We have cats at home but there is no contact so I hope it will be afraid of other animals. At the moment this is our main concern. We don't want to take care of it and then release it completely not afraid and unprepared.
- We will open the door for the sun room in the spring and we will keep everything inside if it want to come back and hide during the transition.
- We also plan to leave some food near the sun room at the beginning.

So if you have any advise, pointers it will be appreciated.
Thank you.